Fiber reinforced ceramic matrix composite internal combustion engine exhaust manifold

ABSTRACT

An exhaust manifold for an engine is made of all fiber reinforced ceramic matrix composite material so as to be light weight and high temperature resistant. A method of making the exhaust manifold comprises the steps of forming a liner of a cast monolithic ceramic material containing pores, filling the pores of the cast monolithic ceramic material with a pre-ceramic polymer resin, coating reinforcing fibers with an interface material to prevent a pre-ceramic polymer resin from adhering strongly to the reinforcing fibers, forming a mixture of a pre-ceramic polymer resin and reinforcing fibers coated with the interface material, forming an exhaust manifold shaped structure from the mixture of the pre-ceramic polymer resin and the reinforcing fibers coated with the interface material by placing the mixture on at least a portion of the cast monolithic ceramic material, and firing the exhaust component shaped structure at a temperature and a time sufficient to convert the pre-ceramic polymer resin to a ceramic thereby forming a reinforced ceramic composite.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to parts of an internal combustion engine or thelike and, more particularly, to apparatus for ducting the exhaustemissions of an internal combustion engine comprising; a plurality ofheader pipes connected to and receiving exhaust gases from the pluralityof the exhaust ports of the engine; and an outlet therefrom connected toan exhaust pipe. More specifically, the invention relates to a breakageresistant, high temperature resistant, corrosion resistant, low heatrejection, structural fiber reinforced ceramic matrix composite exhaustmanifold for internal combustion engine applications.

2. Background Art

For many years, the exhaust systems of internal combustion engines haveremained substantially unchanged. There is a metal exhaust manifold,typically cast iron or steel, or tubular steel, that collects theexhaust gases emitted from the exhaust ports of the engine and outputsthem into a single exhaust pipe. Typically, a muffler, and/or acatalytic converter device is disposed in-line with the exhaust pipe toreduce noise and pollutants associated with engine operation. A typicalprior art exhaust manifold design is depicted in simplified form in FIG.1 where it is generally indicated as 10. There are a plurality offlanges 12 which are bolted or clamped over the exhaust ports (notshown) of the engine (also not shown). The flanges connect individualheader pipes 14 to a common outlet pipe 16 which leads and is connectedto the exhaust system (not shown) at 18. Since good (minimalrestriction) exhaust gas flow is important in overall engineperformance, the curves of the pipes, the interior smoothness, and thelike, are factors considered by designers thereof. Such factors aresomewhat relevant to the novelty of the present invention but will notbe addressed herein in favor of simplified drawings which clearly pointout the true novelty in a manner easily understood by those of ordinaryskill in the art.

Most early and present prior art exhaust manifolds were totally of metalas indicated in FIG. 2. Commercial manifolds were/are generally of castiron or cast steel while specialty manifolds for high performanceengines and the like were/are of welded steel or stainless steel pipe soas to provide a "tuned" exhaust as known to those skilled in the art.Engine designers continue to have difficulties with current exhaustmanifolds of metal design in two distinct arenas. First, during heavyload engine operation exhaust gases can be in excess of 1400° F. whilethe engine block that it is mechanically connected to is held to amaximum of 300° F. by the water cooling system. If a cast iron exhaustmanifold is allowed to get too hot, the manifold can warp or even crackdue to the large loads introduced into it from the large differences inthermal expansion between the two mechanically connected parts. This isdue to its higher temperature. The manifold wants to thermally grow to amuch larger size than the mechanical connection to the block will allow.This failure allows raw exhaust gases into the engine compartment. Thisoccurrence typically requires replacement of, or removal and repair of,the manifold. Although this is not a well known problem, those skilledin the art of engine design will agree that it is a continuing dilemma.Current technology approaches to alleviating the problem are to utilizea much higher cost stainless steel, which has a substantially lowercoefficient of thermal expansion than cast iron, or to reduce theoverall temperature of the exhaust manifold by increasing the heatrejected back to the block at the mounting flanges, or to segment theexhaust manifold into sections that slide inside one another so as toprovide the manifold with the ability to grow. The segmented exhaustmanifolds, however, tend to leak at the joints over time. The secondmajor arena of difficulty for engine designers comes primarily in themarine industry. Here, regulatory requirements dictate maximum allowableengine compartment temperatures and engine "touch" temperatures forin-board marine applications. This typically requires the use of watercooled exhaust manifolds to achieve the regulatory constraints. The mainproblem associated with this approach is corrosion of the metalmanifold. As a result, water-cooled cast iron manifolds must be replacedmuch more often than desirable; or, the manifolds must be manufacturedof a much more costly stainless steel material.

More recently, for use with engines having higher operatingtemperatures, the addition of a ceramic liner 20, as shown in FIG. 3,has been suggested. For this, the prior art suggests only the use of amonolithic ceramic material. See, for example, the 1995 patent of FordMotor Company to Hartsock (U.S. Pat. No. 5,404,721).

In another co-pending application entitled METHODS AND APPARATUS FORMAKING CERAMIC MATRIX COMPOSITE LINED AUTOMOTIVE PARTS AND FIBERREINFORCED CERAMIC MATRIX COMPOSITE AUTOMOTIVE PARTS by the inventorsherein U.S. Ser. No. 08/515,849, filed on Aug. 16, 1995 and assigned tothe common assignee of this application, an improved structural fiberreinforced ceramic matrix composite (FRCMC) material is disclosed forlining metal parts such as exhaust manifolds which does not suffer fromthe problems of failure due to thermal shock, damage from minor impacts,or erosion of a monolithic ceramic liner the following is a summary ofthe above co-pending patent application, the teachings of which areincorporated herein by reference.

SUMMARY OF METHODS AND APPARATUS FOR MAKING CERAMIC MATRIX COMPOSITELINED AUTOMOTIVE PARTS AND FIBER REINFORCED CERAMIC MATRIX COMPOSITEAUTOMOTIVE PARTS

A first aspect of the present invention is a method for forming a metalpart having a breakage resistant ceramic liner comprising the steps of,forming a metal part having a mating surface for receiving the liner;forming a liner of a ceramic material containing pores; filling thepores with a pre-ceramic polymer resin; firing the pre-ceramic polymerresin saturated liner at a temperature and for a time (designated by theresin manufacturer) which converts the resin into a ceramic within thepores; and, bonding the ceramic liner to the mating surface of the metalpart.

In one embodiment, the step of forming the liner of a ceramic materialcontaining pores comprises pouring an inexpensive castable cementatiousslurry into a liner-shaped mold, firing the molded slurry material for atime and at a temperate which converts it into a handleable pre-ceramicform, removing the pre-ceramic form from the mold, and firing thepre-ceramic form for a time and at a temperate which converts it into aceramic form containing pores formed by out-gassing. And, the step offilling the pores with a polymer-derived ceramic resin comprises placingthe liner into a bath containing a liquid pre-ceramic polymer resinuntil the pores are saturated with the resin. Preferably, the resin issilicon-carboxyl resin (sold by Allied-Signal under the trade nameBlackglas).

In a second embodiment, the step of forming the liner of a ceramicmaterial containing pores comprises positioning a fiber preform into aliner-shaped mold to occupy 30% to 60% of the volume of the mold,forcing a liquid pre-ceramic polymer resin through the preform to fillthe remaining volume of the mold with the liquid pre-ceramic polymerresin, firing the mold for a time and at a temperate which converts itinto a handleable pre-ceramic form, removing the pre-ceramic form fromthe mold, and firing the pre-ceramic form for a time and at a temperatewhich converts the liquid pre-ceramic polymer resin into a ceramicmatrix composite form containing pores formed by outgassing. Preferably,the liquid pre-ceramic polymer resin is silicon-carboxyl resin, e.g.Blackglas.

A second aspect of the present invention is a method for forming a metalpart having a breakage resistant ceramic liner comprising the steps of,forming a liner of a ceramic material containing pores; filling thepores with a pre-ceramic polymer resin; firing the pre-ceramic polymerresin saturated liner at a temperature and for a time (as designated bythe resin manufacturer), which converts the resin into a ceramic withinthe pores; positioning the liner within a mold for the metal part withthe mating surface of the liner facing into a portion of the mold to beoccupied by the metal forming the part; and, filling the mold withmolten metal to form the part.

As with the first aspect, the step of forming the liner of a ceramicmaterial containing pores can comprise either approach described above.And, the step of filling the pores with a polymer-derived ceramic resinagain comprises placing the liner into a bath containing a liquidpre-ceramic polymer resin until the pores are saturated with the resin;firing the pre-ceramic polymer resin saturated liner at a temperatureand for a time which converts the resin into a ceramic within the pores.

In all cases where the pores formed by outgassing are filled, it ispreferred to repeat the pore-filling and re-heating process severaltimes to virtually totally remove the pores from the final product.

In another aspect of the present invention, a method of making a fiberreinforced ceramic matrix composite automotive part is disclosedcomprising the steps of, forming a preform in the shape of the part fromfibers of a generic fiber system employable in fiber reinforced ceramicmatrix composites; placing the preform in a cavity of a mold having theshape of the part; forcing a liquid polymer-derived ceramic resinthrough the cavity to fill the cavity and saturate the preform; heatingthe mold at a temperature and for a time associated with thepolymer-derived ceramic resin which transforms the liquidpolymer-derived ceramic resin-saturated preform into a polymer compositepart; removing the polymer composite part from the mold; and, firing thepolymer composite part in an inert atmosphere at a temperature and for atime associated with the polymer-derived ceramic resin which transformsthe polymer-derived ceramic resin into a ceramic whereby the polymercomposite part is transformed into a fiber reinforced ceramic matrixcomposite part.

Preferably, the method also includes the steps of, immersing the fiberreinforced ceramic matrix composite part containing pores formed byoutgassing during firing into a bath of the liquid polymer-derivedceramic resin to fill the pores with the liquid polymer-derived ceramicresin; firing the fiber reinforced ceramic matrix composite part in aninert atmosphere at a temperature and for a time associated with thepolymer-derived ceramic resin which transforms the polymer-derivedceramic resin in the pores into a ceramic; and, repeating this processuntil the pore density within the final fiber reinforced ceramic matrixcomposite part is less than a pre-established percentage affordingmaximum strength to the part.

The preferred method is also adaptable to forming hollow parts such asengine manifolds by employing the steps of, forming a first preform inthe shape of a lower portion of the manifold from fibers of a genericfiber system employable in fiber reinforced ceramic matrix composites;placing the first preform in a cavity of a first mold having the shapeof the lower portion of the manifold; forcing a liquid polymer-derivedceramic resin through the cavity to fill the cavity and saturate thefirst preform; heating the first mold at a temperature and for a timeassociated with the polymer-derived ceramic resin which transforms theliquid polymer-derived ceramic resin-saturated first preform into afirst polymer composite part; removing the first polymer composite partfrom the mold; forming a second preform in the shape of an upper portionof the manifold from fibers of the generic fiber system; placing thesecond preform in a cavity of a second mold having the shape of theupper portion of the manifold; forcing the liquid polymer-derivedceramic resin through the cavity to fill the cavity and saturate thesecond preform; heating the second mold at a temperature and for a timeassociated with the polymer-derived ceramic resin which transforms theliquid polymer-derived ceramic resin-saturated second preform into asecond polymer composite part; removing the second polymer compositepart from the mold; fitting the first polymer composite part and thesecond polymer composite part together along mating edges to form themanifold as a hollow conduit-shaped part; and, firing the polymercomposite manifold in an inert atmosphere at a temperature and for atime associated with the polymer-derived ceramic resin which transformsthe polymer-derived ceramic resin into a ceramic whereby the polymercomposite manifold is transformed into a fiber reinforced ceramic matrixcomposite manifold and the upper portion and the lower portion are fusedtogether along the mating edges. Pores formed by outgassing arepreferably sealed in the manner described above to give maximum strengthto the resultant manifold and seal any leakage that may exist along themating edges.

Where the manifold is an exhaust manifold to be internally filled with aceramic foam catalyst substrate structure the process and requiredtooling can be greatly simplified by prior to the step of placing thesecond preform in a cavity of a second mold having the shape of theupper portion of the manifold additionally including the steps of,placing the first preform as part of a cavity-defining wall of thesecond mold; and, placing the ceramic foam catalyst substrate structurein the first preform whereby the first preform and the ceramic foamcatalyst substrate structure in combination form part of the cavity ofthe second wall. In the interest of engine weight, and the like, anexhaust manifold entirely of a ceramic material would be highlydesirable.

Wherefore, it is the object of the present invention to provide such anexhaust manifold made entirely of a structural fiber reinforced ceramicmatrix composite (FRCMC) material.

Other objects and benefits of this invention will become apparent fromthe description which follows hereinafter when read in conjunction withthe drawing figures which accompany it.

SUMMARY OF THE DISCLOSURE

The foregoing objects have been achieved in an exhaust manifold for aninternal combustion engine having a plurality of header pipes to beconnected to and receiving exhaust gases from respective ones of aplurality of exhaust ports of the engine and a single outlet to beconnected to an exhaust pipe or system wherein the exhaust manifold isof a structural fiber reinforced ceramic matrix composite materialcomprising fibers of a generic fiber system that have been coated with ageneric interface material disposed throughout a ceramic matrix.

The preferred resin to create the ceramic matrix is either of the twopolymer-derived ceramic resins (hereinafter used interchangeably withthe term pre-ceramic polymer resin) comprising silicon-carboxyl andalumina silicate or a cementatious resin that has been modified toemulate the processing methods of typical structural polymer compositesystems such as monoaluminum phosphate (also know as monoaluminophosphate) resin. The preferred generic fiber system comprises alumina,Altex, Nextel 312, Nextel 440, Nextel 510, Nextel 550, silicon nitride,silicon carbide, HPZ, graphite, carbon and peat. The preferred genericinterface material comprises carbon, silicon nitride, silicon carboxyl,silicon carbide or boron nitride or a layered combination of one or moreof the above interfacial materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of a typical exhaust manifoldstructure.

FIG. 2 is a cross section through the exhaust manifold of FIG. 1 in theplane II/III/IV--II/III/IV when the manifold is a prior art metalmanifold.

FIG. 3 is a cross section through the exhaust manifold of FIG. 1 in theplane II/III/IV--II/III/IV when the manifold is a prior art metalmanifold having a monolithic ceramic liner on the inner walls thereof.

FIG. 4 is a cross section through the exhaust manifold of FIG. 1 in theplane II/III/IV--II/III/IV when the manifold is an all FRCMC manifoldaccording to the present invention.

FIG. 5 is a partially cutaway drawing of a mold showing how the allFRCMC manifold of the present invention can have additional structuralmetal members attached thereto by molding them in place.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention and as also employed in the enginementioned above, the exhaust manifold 10' of FIG. 4 is made entirelyfrom a FRCMC structure that eliminates the strain intolerance and notchsensitivity of conventional prior art monolithic ceramic structures. TheFRCMC of this invention employs any of several polymer-derived ceramicresins commercially available such as silicon-carboxyl resin (sold byAllied-Signal under the trade name Blackglas), alumina-silicate resin(sold by Applied Poleramics under the trade name CO2) or cementatoussystems that have been modified to emulate the processing methods oftypical structural polymer composite systems such as monoaluminumphosphate (aka monoalumino phosphate) resin combined with a genericfiber system (hereinafter used interchangeably with the term reinforcingfibers such as, but not limited to, alumina, Altex, Nextel 312, Nextel440, Nextel 510, Nextel 550, Silicon Nitride, Silicon Carbide, HPZ,Graphite, Carbon, and Peat. To accomplish the objectives of the presentinvention, the fiber system is first coated to 0.1 to 5.0 micronsthickness with an interface material such as, but not limited to,carbon, silicon nitride, silicon carboxyl, silicon carbide, or boronnitride. The interface material prevents the resin from adheringdirectly to the fibers of the fiber system. Thus, when the resin hasbeen converted to a ceramic, there is a weak disbond layer between theceramic and fibers imparting the desired more ductile qualities to thefinal FRCMC.

Thus, according to the present invention, the steps of constructing abreakage resistant, heat resistant, corrosion resistant, low heatrejection, ceramic exhaust manifold comprise applying the interfacematerial on the fiber system as per best industry standards, mixing theinterface-coated fiber system with the resin, forming the manifold asper best industry practices used in the fabrication of structuralpolymer composite hardware, and firing the resultant part at a hightemperature per material supplier specifications to convert the resininto a ceramic.

There are a number of distinct advantages offered by a FRCMC internalcombustion engine exhaust manifold over current metal and potentialmonolithic ceramic manifolds, they are as follows:

1) Being that the manifold is a ceramic, it inherently has a betterinsulating capability than it's metallic counterpart, thus reducingengine compartment heat load.

2) Being that the manifold is a ceramic, it has a substantially lowercoefficient of thermal expansion than it's metallic counterpart, thusreducing the thermally induced loads on the manifold from the extremetemperature differential between the engine block and the manifold.

3) Being that the manifold is a ceramic, it is inherently corrosionresistant.

4) Being that the manifold is a ceramic, it inherently is moretemperature resistant than it's metallic counterpart.

5) Being that the manifold is a ceramic, it inherently is substantiallylighter than it's metallic counterpart (FRCMC is lower density thanaluminum, i.e. approximately 0.08 pounds/cubic inch).

6) Being that the manifold is a fiber reinforced composite with a fiberinterface coating, it is substantially more strain tolerant (ductile)than it's monolithic ceramic counterpart.

7) Being that the manifold is a fiber reinforced composite with a fiberinterface coating, it is substantially less notch sensitive than it'smonolithic ceramic counterpart.

8) Being that the manifold is a fiber reinforced composite with a fiberinterface coating, it is substantially more breakage resistant than it'smonolithic ceramic counterpart.

9) Being that the manifold is a fiber reinforced composite with a fiberinterface coating, it's strength characteristics can be tailored viachoice of fiber, interface coating, and fiber orientation.

10) Being that the manifold is a fiber reinforced composite with a fiberinterface coating, it's coefficient of thermal expansion can be tailoredto better match that of the engine block via selection of fiber system.

11) Being that the manifold is a fiber reinforced ceramic matrixcomposite with a fiber interface coating, it's material properties donot degrade as a function of temperature in the manifold operatingtemperature range as does it's metallic counterpart.

12) Being that the manifold is a fiber reinforced ceramic matrixcomposite with a fiber interface coating, it is more resistant to damageresulting from thermal shock than it's monolithic ceramic counterpart.

EXAMPLE Fabrication of a FRCMC Exhaust Manifold

1. Lay-up either a pair of half-manifolds (upper and lower halves) to bejoined at a later step or a total manifold, from woven cloth matting ofone the fibers that are identified in co-pending application U.S. Ser.No. 08/515,604, filed on Aug. 16, 1995 entitled HIGH EFFICIENCY,LOW-POLLUTION ENGINE by the common inventors of this application andassigned to the same assignee, the teachings of which are incorporatedherein by reference.

2. The half-manifolds or total manifold fiber perform then have a fiberinterface coating applied as per industry best practices. The fibercould have been coated prior to forming the fiber manifold shapes. Theassignee of this application, Northrop Corporation, currently has anumber of patents on the application of interface coatings, including,U.S. Pat. No. 5,034,181, entitled APPARATUS FOR METHOD OF MANUFACTURINGPREFORMS; U.S. Pat. No. 5,110,771, entitled METHOD OF FORMING APRECRACKED FIBER COATING FOR TOUGHENING CERAMIC FIBER-MATRIX COMPOSITES;U.S. Pat. No. 5,275,984, entitled FIBER COATING OF UNBONDED MULTI-LAYERSFOR TOUGHENING CERAMIC FIBER-MATRIX COMPOSITES; U.S. Pat. No. 5,162,271,entitled METHOD OF FORMING A DUCTILE FIBER COATING FOR TOUGHENINGNON-OXIDE CERAMIC MATRIX COMPOSITES; and U.S. Pat. No. 5,221,578,entitled WEAK FRANGIBLE FIBER COATING WITH UNFILLED PORES FOR TOUGHENINGCERAMIC FIBER-MATRIX COMPOSITES the teachings of which are incorporatedherein by reference. Also, Allied-Signal or Sinterials are commercialcompanies which will apply an interface coating as a purchased service.

3. The half-manifolds or total manifold are then saturated with theresin, in this example being Blackglas resin. This step may also includesqueezing the mixture of polymer-derived ceramic resin and interfacematerial-coated fibers of a generic fiber system under pressure into amold to form the manifold shaped structure.

4. The resin-saturated half-manifolds or total manifold is then heatedas per the following cycle:

A) Ramp from ambient to 150° F. at 2.7°/minute

B) Hold at 150° F. for 30 minutes

C) Ramp at 1.7°/minute to 300° F.

D) Hold at 300° F. for 60 minutes

E) Cool at 1.2°/minute until temperature is below 140° F.

It should be noted that there are a variety of heat-up cycle definitionswhich will create usable hardware and the foregoing is by way of oneexample only and not intended to be exclusive.

5. If half-manifolds were made, they are snapped or fitted togetheralong mating edges at this point to form a total manifold. The twopieces now fitted together are dipped in Blackglas resin for a minimumof five minutes. The part is then removed from the resin and heated asper the previous ramp-up rate to hold the edges together.

6. The polymer composite manifold is then pyrolized. In this regard,fabrication of a sealable container, such as a stainless steel box,capable of withstanding 1900° F. is required for the pyrolysis cycle ina standard furnace. In the alternative, an inert gas furnace could beused if available. The box should have two tubing connections, one onthe bottom and one on the top to allow the box to be flooded with aninert gas. In this example, the manifold is placed in the box, the boxplaced in a standard furnace, stainless steel tubing is connected to thelower connector on the box and to a supply of high purity argon. Anyequivalent inert gas could, of course, be used. The argon is allowed toflow into the box, and out the top vent at a rate of 5-10 standard cubicfeet per hour for the entire heat cycle, thus assuring the manifold istotally enveloped in an inert environment. The furnace is closed andfired on the following basis:

A) Ramp to 300° F. at 223°/hour

B) Ramp to 900° F. at 43°/hour

C) Ramp to 1400° F. at 20°/hour

D) Ramp to 1600° F. at 50°/hour

E) Hold at 1600° F. for 4 hours

F) Ramp to 77° F. at -125°/hour

Again, there are a variety of heating schedules other than this one,given by way of example only, which will yield usable product.

7. Upon cooling, the manifold is removed from the furnace and box andsubmerged in a bath of Blackglas resin for enough time to allow all airto be removed from the manifold (typically 5 minutes or more). A vacuuminfiltration step may also be used for this step. This fills any porescaused by outgassing or shrinkage of the matrix in the FRCMC manifoldwith the resin.

8. Steps 6 and 7 are then repeated until the level of porosity is belowa desired level which imparts the maximum strength to the final FRCMCmanifold. Typically, it is preferred that this cycle be repeated fivetimes. The manifold is then ready for use.

FIG. 5 depicts an alternate aspect of the present invention which can beemployed, if desired, to augment the strength of the resultant manifold.Being a ceramic material, the manifold 10' can be subjected to moltenmetal without damage. Thus, one can make a basic manifold 10' asdescribed above which does not have completed flanges 12, for example.As depicted in FIG. 5, the basic manifold 10' is then positioned withina mold 22. Molten metal 24 is then poured into the mold 22. The metal 24flows around the encased portions of the FRCMC manifold 10' capturingthem within the metal as it hardens thus forming the flanges 12 and/or,if desired, a strong-back system 26 which can be bolted to theautomobile to support the manifold 10' against excessive bending forcesfrom the exhaust system and the like.

Wherefore, having thus described the present invention, what is claimedis:
 1. A method of making a high temperature resistant fiber reinforcedceramic matrix composite exhaust manifold for an engine comprising thesteps of:a) forming a liner of a cast monolithic ceramic materialcontaining pores; b) filling the pores of the cast monolithic ceramicmaterial with a pre-ceramic polymer resin; c) coating reinforcing fiberswith an interface material to prevent a pre-ceramic polymer resin fromadhering strongly to the reinforcing fibers; d) forming a mixture of apre-ceramic polymer resin and reinforcing fibers coated with theinterface material; e) forming an exhaust manifold shaped structure fromthe mixture of the pre-ceramic polymer resin and the reinforcing fiberscoated with the interface material by placing the mixture on at least aportion of the cast monolithic ceramic material; and, f) firing theexhaust component shaped structure at a temperature and a timesufficient to convert the pre-ceramic polymer resin to a ceramic therebyforming a reinforced ceramic composite.
 2. The method of claim 1 whereinsaid step of coating reinforcing fibers with an interface materialcomprises:coating the reinforcing fibers with 0.1 to 5.0 micronsthickness of at least one layer of the interface material of at leastone of carbon, silicon nitride, silicon carbide, silicon carboxide, orboron nitride.
 3. The method of claim 1 wherein said step of coatingreinforcing fibers with an interface material comprises:coatingreinforcing fibers of at least one of alumina, high purity alumina,alumina boro silicate, mullite, alumina silicate, silicon nitride,silicon carbide, carbon, or peat with the interface material.
 4. Themethod of claim 1 wherein said step of forming a mixture of thepre-ceramic polymer resin and the reinforcing fibers coated with theinterface material comprises:mixing the reinforcing fibers coated withthe interface material with a material chosen from the group consistingof pre-ceramic polymer resins commercially available such assilicon-carboxyl resin, alumina-silicate resin or monoaluminum phosphateresin.
 5. The method of claim 1 wherein said step of forming an exhaustmanifold shaped structure from the mixture of the pre-ceramic polymerresin and reinforcing fibers coated with the interface materialcomprises:squeezing the mixture of the pre-ceramic polymer resin and thereinforcing fibers coated with the interface material under pressureinto a mold to form the manifold shaped structure prior to firing. 6.The method of claim 1 and, after said step (f) thereof of firingadditionally comprising the steps of:a) positioning the ceramic manifoldin a mold; and, b) pouring molten metal into the mold around portions ofthe ceramic manifold to add additional structural components of metal tothe ceramic manifold.
 7. The method of claim 1 wherein said step ofcoating reinforcing fibers with an interface material comprises:coatingreinforcing fibers with the interface material, wherein said reinforcingfibers comprises ceramic fibers capable of withstanding high processingtemperatures associated with converting the pre-ceramic polymer resin toa ceramic matrix in an inert environment.
 8. The method of claim 4wherein said step of forming a mixture of pre-ceramic polymer resin andthe reinforcing fibers coated with the interface materialcomprises:mixing the reinforcing fibers coated with the interfacematerial with a modified cementatous pre-ceramic polymer resin.
 9. Themethod of claim 1 wherein the step of forming an exhaust manifoldcomprises:forming an exhaust manifold shaped structure from the mixtureof the pre-ceramic polymer resin and the reinforcing fibers coated withthe interface material by placing the mixture on an inside portion ofthe cast monolithic ceramic material.
 10. The method of claim 1 whereinthe step of forming an exhaust manifold comprises:forming an exhaustmanifold shaped structure from the mixture of the pre-ceramic polymerresin and the reinforcing fibers coated with the interface material byplacing the mixture on an outside portion of the cast monolithic ceramicmaterial.
 11. The method of claim 1 wherein the step of forming anexhaust manifold comprises:forming an exhaust manifold shaped structurefrom the mixture of the pre-ceramic polymer resin and the reinforcingfibers coated with the interface material by placing the mixture aroundthe cast monolithic ceramic material.
 12. A method of making a hightemperature resistant fiber reinforced ceramic matrix composite exhaustmanifold for an engine comprising the steps of:a) forming a liner of acast monolithic ceramic material containing pores; b) filling the poresof the cast monolithic ceramic material with a pre-ceramic polymerresin; c) coating reinforcing fibers with an interface material toprevent a pre-ceramic polymer resin from adhering directly to thereinforcing fibers, the reinforcing fibers comprising fibers of at leastone of alumina, high purity alumina, alumina boro silicate, mullite,alumina silicate, silicon nitride, silicon carbide, HPZ, graphite,carbon, or peat, the interface material comprising a few micronsthickness of at least one of carbon, silicon nitride, silicon carbide,silicon carboxide, or boron nitride; d) forming a mixture of apre-ceramic polymer resin chosen from the group consisting ofsilicon-carboxyl resin, monoaluminum phosphate resin, or aluminasilicate resin and the reinforcing fibers coated with the interfacematerial; e) forming an exhaust manifold shaped structure from themixture of the pre-ceramic polymer resin and the reinforcing fiberscoated with the interface material by placing the mixture on at least aportion of the cast monolithic ceramic material; and, f) firing theexhaust manifold shaped structure at a temperature and for a timesufficient to convert the pre-ceramic polymer resin to a ceramic therebyforming a reinforced ceramic composite.
 13. The method of claim 12wherein said step of forming a mixture of a pre-ceramic polymer resinand reinforcing fibers coated with the interface materialcomprises:saturating a woven cloth matting of the reinforcing fiberscoated with the interface material and the pre-ceramic polymer resin.14. The method of claim 13 wherein said step of forming an exhaustmanifold shaped structure from the mixture of the pre-ceramic polymerresin and the reinforcing fibers coated with the interface materialadditionally includes the step of:squeezing the woven cloth matting ofthe reinforcing fibers coated with the interface material and saturatedwith the pre-ceramic polymer resin in a mold under pressure prior tofiring.
 15. The method of claim 12 and, after said step (f) of firingadditionally comprising the steps of:(1) positioning the manifold in amold; and, (2) pouring molten metal into the mold around portions of themanifold to add additional structural metal components to the manifold.16. The method of claim 12 wherein the step of forming an exhaustmanifold comprises:forming an exhaust manifold shaped structure from themixture of the pre-ceramic polymer resin and the reinforcing fiberscoated with the interface material by placing the mixture on an insideportion of the cast monolithic ceramic material.
 17. The method of claim12 wherein the step of forming an exhaust manifold comprises:forming anexhaust manifold shaped structure from the mixture of the pre-ceramicpolymer resin and the reinforcing fibers coated with the interfacematerial by placing the mixture on an outside portion of the castmonolithic ceramic material.
 18. The method of claim 12 wherein the stepof forming an exhaust manifold comprises:forming an exhaust manifoldshaped structure from the mixture of the pre-ceramic polymer resin andthe reinforcing fibers coated with the interface material by placing themixture around the cast monolithic ceramic material.
 19. A method ofmaking a high temperature resistant fiber reinforced ceramic matrixcomposite exhaust manifold for an engine comprising the steps of:a)forming a liner of a cast monolithic ceramic material containing pores;b) filling the pores of the cast monolithic ceramic material with apre-ceramic polymer resin; c) coating reinforcing fibers with aninterface material to prevent a pre-ceramic polymer resin from adheringdirectly to the reinforcing fibers, the reinforcing fibers comprisingfibers of at least one of alumina, high purity alumina, alumina borosilicate, mullite, alumina, silicate, silicon nitride, silicon carbide,HPZ, graphite, carbon, or peat, the interface material comprising 0.1 to5.0 microns thickness of at least one of carbon, silicon nitride,silicon carbide, silicon carboxide, or boron nitride; d) forming amixture of silicon-carboxyl resin and the reinforcing fibers coated withthe interface material; e) forming an exhaust manifold shaped structurefrom the mixture of the silicon-carboxyl resin and the reinforcingfibers coated with the innerface material by placing the mixture on atleast a portion of the cast monolithic ceramic material; and, f) firingthe exhaust manifold shaped structure at a temperature and for a timesufficient to convert the silicon-carboxyl to a ceramic.
 20. The methodof claim 19 wherein said step of forming a mixture of silicon-carboxylresin and reinforcing fibers coated with the interface materialcomprises:saturating a woven cloth matting of the reinforcing fiberscoated with the interface material with the silicon-carboxyl resin. 21.The method of claim 20 wherein said step of forming an exhaust manifoldshaped structure from the mixture of the silicon-carboxyl resin andreinforcing fibers coated with the interface material additionallyincludes the step of:squeezing the woven cloth matting of thereinforcing fibers coated with the interface material and saturated withthe silicon-carboxyl resin in a mold under pressure prior to firing. 22.The method of claim 19 and, after said step (f) of firing additionallycomprising the steps of:(1) immersing the fired manifold into a bath ofsilicon-carboxyl resin to fill pores formed by outgassing therein withthe silicon-carboxyl resin; (2) refiring the manifold at a temperatureand for a time sufficient to convert the silicon-carboxyl to a ceramic;and, (3) repeating steps (1) and (2) until the remaining volume of poresformed by outgassing is below an amount which maximizes the strength ofthe manifold.
 23. The method of claim 19 and, after said step (f) offiring additionally comprising the steps of:(1) positioning the manifoldin a mold; and, (2) pouring molten metal into the mold around portionsof the manifold to add additional structural metal components to themanifold.
 24. The method of claim 23 and, after said step (e)additionally comprising the steps of:(1) positioning the manifold in amold; and, (2) pouring molten metal into the mold around portions of themanifold to add additional structural metal components to the manifold.25. The method of claim 19 wherein the step of forming an exhaustmanifold comprises:forming an exhaust manifold shaped structure from themixture of the pre-ceramic polymer resin and the reinforcing fiberscoated with the interface material by placing the mixture on an insideportion of the cast monolithic ceramic material.
 26. The method of claim19 wherein the step of forming an exhaust manifold comprises:forming anexhaust manifold shaped structure from the mixture of the pre-ceramicpolymer resin and the reinforcing fibers coated with the interfacematerial by placing the mixture on an outside portion of the castmonolithic ceramic material.
 27. The method of claim 19 wherein the stepof forming an exhaust manifold comprises:forming an exhaust manifoldshaped structure from the mixture of the pre-ceramic polymer resin andthe reinforcing fibers coated with the interface material by placing themixture around the cast monolithic ceramic material.